1. Field of the Invention
The present invention relates to methods for manufacturing a water hammer arrester, more particularly to methods for manufacturing a water hammer arrester having not only an endurance capable of withstanding a hydraulic pressure but also an excellent productivity.
2. Discussion of Related Art
In general, a phenomenon such as water-hammer happens at such a place as a bent part of a pipeline through which a fluid passes, that is to say, where a flow of a fluid is cut off. This water-hammer may cause a big noise as well as a big vibration which can damage the pipeline and further is well known to be a primary factor of the reduction of a building's life span.
A water hammer arrester is installed in a pipeline to protect the pipeline against the water hammer. The water hammer arrester includes a cylinder-shaped chamber, an end of which is connected to the pipeline while the other end thereof is hermetically closed, and a piston moving within a housing to correspond to a pressure change of a fluid running along the pipeline and a nipple for connecting the housing with the pipeline. Consequently, the housing, an upper end of which is hermetically closed, consists of a cylinder having commonly a predetermined length because the piston should be operated within the housing by the way of a stroke.
The water hammer arrester having this housing is illustrated in Joserb P. Isrnet et al. U.S. Pat. No. 4,819,698 and in Charles H. Perrott et al. U.S. Pat. No. 5,385,172.
In Joserb P. Isrnet et al. U.S. Pat. No. 4,819,698, as shown in FIG. 1, a water hammer arrester 201 is provided with a chamber 202 made of elongated alloyed material which includes an upper end 203 closed on the whole jointless and a lower end 204 capable of being connected to a distributing pipe 210.
In a chamber 202, a piston 215 defines an upper part of a chamber, which has a super atmospheric charge of gas giving a downward inclining pressure to the piston 215. The piston 215 is made not to be infiltrated by a fluid or a gas and made of light compound material and provided with at least 3 O-rings 219-221 in the circumference thereof for the prevention of a gas or fluid leakage of an upper as well as a lower part of the chamber. The piston 215 is desirably formed in a dome 224 according to the shape of an inner upper end 227 and formed in the hollow to collect sediment when used as in upside down orientation.
In the meanwhile, Charles H. Perrott et al. U.S. Pat. No. 5,385,172, as shown in FIG. 2, relates to a jointless water hammer arrester, an end of which 122 is closed and includes a hollow cylinder 120 made of brass or other proper metal. A piston 124 is freely slid within the cylinder 120, while a circumference surface of the piston 124 includes ring-holes 128 and an closing rings 130 which is engaged with the holes 128. The closing rings 130 are made of natural or compound rubber, plastics or other proper material.
A connector 134 connecting the water hammer arrester to a system conducting a fluid is mounted on an open end of the cylinder 120 by means of soldering or by other proper means. The connector 134 is provided with a cap 136 or a cylinder inserted onto the open end portion of the cylinder 120 in series by soldering as well as a screw part 138.
As shown FIGS. 3a-3c, Joserb P. Isrnet et al. U.S. Pat. No. 4,819,698 relates to method for manufacturing a housing (cylinder). As shown in FIG. 3a, a cylinder having two open ends 301 is precessed into a semi-circular shape, as shown in FIG. 3b, in order for an end thereof to form a dome 302. Accordingly, an end of the cylinder 301 being processed to form dome 302 has a thinner thickness than the other parts. Besides, a hole made by the end of the cylinder 301, as shown in FIG. 3b, are formed in the middle of the dome 302. The hole 303, as shown in FIG. 3c, are closed using a welding machine and so formed into a complete dome 302.
However, as the method for manufacturing a housing of the above described conventional water hammer arrester can cause the cylinder 301, which is for making the housing, may be deformed by welding and requires a highly skilled worker who can finish welding in a short time to minimize the deformation.
FIG. 4a-4b illustrate the method for manufacturing a housing (cylinder) according to Charles H. Perrott et al. U.S. Pat. No. 5,385,172. The cylinder 301 having two opened ends, is closed by a cap 310 made of identical material and the cap 310 is cut by a processor means such as a lathe in order to have a plug 311 inserted into an upper end of the cylinder 301 in the lower part. The plug 311, as shown in the drawings, has a smaller diameter than the inner diameter of the cylinder 301 and is processed so that an edge part of circumference 312 has a fixed angle. In addition, there are indents 313 in the boundary between the plug 311 and the cap 310.
As shown in FIG. 4b, the cap 310 is inserted into the upper end of the cylinder 301, before the cap 310 is completely fixed to the upper portion of the cylinder 301 by welding from the inside of the cylinder 301.
As the housing of the water hammer arrester has the inside, there is some merit that it looks neat externally. Still, as a cutting work has to be firstly carried out to process the cap, the cost of production is increased. Furthermore, as the cap is welded inside the cylinder, a lot of bad welds occur. Consequently, it causes the price of goods to go up.